How to keep a mesh in the same location relative to its parent mesh?
The letters and the "buttons" are two separate object. In order to get them move together, they should be one object. One "m" should be joined with one "button". 

First, select every "m" individually, then hit Ctrl+A and select "Rotation and Scale". Repeat this for every "m" and every "button". 

Select the "m", then shift-select the "button", then hit Ctrl+J to join them. Repeat this for all six pairs.